• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.235-240
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• 2001

The CHFG (Critical Heat Flux in Gap) test results have been evaluated to quantify the critical power in hemispherical narrow gaps and a new correlation has been developed. The CHFG test results have shown that increases in the gap thickness and pressure lead to an increase in critical power. The pressure effect on the critical power was found to be much milder than predictions by CHF correlations of other researches. From the CHFG test results, a new correlation on critical power in the hemispherical gap has been developed using the non-dimensional parameters as follows: $$\frac{qCHF}{{\rho}g^hfg}{\cdot}4\sqrt{\frac{{\rho}_g^2}{g{\sigma}{\Delta}{\rho}}=\frac{0.1042}{1+0.1375({\rho}g/{\rho}l)^{0.21}(D/s)}$$ The developed correlation has been expanded to apply the spherical geometry using the Siemens/KWU's correlation.

• 한국통신학회논문지
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• 제31권2C호
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• pp.191-199
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• 2006

본 논문에서는 OFDM 신호의 높은 PAPR과 전력 증폭기의 비선형성에 의한 신호의 왜곡과 스펙트럼의 확산을 방지하기 위하여 $rho$차 역필터 구조를 사용하는 전치 보상기를 구현하는 방안을 제시한다. 메모리가 없는 고전력 증폭기를 다항식으로 모델링 하고 전치 보상기로써 비선형 증폭기 특성의 역모델인 $rho$차 역필터 구조를 이용한다. $rho$차 역필터 구조는 비선형 시스템이 다항식으로 모델링 된다면 다항식의 계수만으로 구현될 수 있으므로 많은 메모리가 필요 없다. 비선형 전력 증폭기 모델의 계수 갱신을 위하여는 LMS, RLS 알고리듬을 모두 사용할 수 있으며 계수의 개수가 적어 수렴 속도가 빠르고 복소 계산이 필요 없으므로 계산도 간단하다.

• The Korean Journal of Ecology
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• 제27권1호
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• pp.27-33
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• 2004

Cryptomeria japonica plantation was monitored every year during 15 years from 1983 to 1997 for stem diameter and volume. The reciprocal equation, 1/Y = A + B/N, was applied to the relationship between cumulative volume Y and cumulative number N from the largest tree in the stand each year. The parameters A and B, which means respectively the reciprocal of an asymptotic value of total stand stem volume and the reciprocal of the maximum stem volume, are related by a power function. The power functional relationship between A and B derived a linear relationship of B-points ( $N_{B}$, $V_{B}$; $N_{B}$ = B/A, $Y_{B}$ = 1/2A) of each Y-N curve on log-log coordinates. The gradient of B-point line was so steep that the Y-N curve moved parallel upward year by year. The time trajectory of mean stem volume (W) and density ($\rho$) provided evidence in favor of the 3/2 power law of self-thinning, because the gradient of W - $\rho$ trajectory on log-log coordinates approximated to -3/2 at the final stage of stand development. On the basis of the results of Y-N curves and W - $\rho$ trajectory, the time trajectory of maximum stem volume $W_{max obs}$ and $\rho$ was derived theoretically. The gradient of $W_{max obs}$ - $\rho$ trajectory on log-log coordinates is calculated to be -0.6105 at the final stage. The gradient of $W_{max obs}$ - $\rho$ trajectory was steeper than that of W - $\rho$ trajectory at the early stage, while the former is gentler than the latter at the later stage.stage.e.age.e.

• Journal of the Korean Data and Information Science Society
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• 제15권4호
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• pp.743-752
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• 2004

In this paper, we develop the Bayesian model selection procedure using the reference prior for comparing two nested model such as the independent and intraclass models using the distance or divergence between the two as the basis of comparison. A suitable criterion for this is the power divergence measure as introduced by Cressie and Read(1984). Such a measure includes the Kullback -Liebler divergence measures and the Hellinger divergence measure as special cases. For this problem, the power divergence measure turns out to be a function solely of $\rho$, the intraclass correlation coefficient. Also, this function is convex, and the minimum is attained at $\rho=0$. We use reference prior for $\rho$. Due to the duality between hypothesis tests and set estimation, the hypothesis testing problem can also be solved by solving a corresponding set estimation problem. The present paper develops Bayesian method based on the Kullback-Liebler and Hellinger divergence measures, rejecting $H_0:\rho=0$ when the specified divergence measure exceeds some number d. This number d is so chosen that the resulting credible interval for the divergence measure has specified coverage probability $1-{\alpha}$. The length of such an interval is compared with the equal two-tailed credible interval and the HPD credible interval for $\rho$ with the same coverage probability which can also be inverted into acceptance regions of $H_0:\rho=0$. Example is considered where the HPD interval based on the one-at- a-time reference prior turns out to be the shortest credible interval having the same coverage probability.

• Journal of the Korean Data and Information Science Society
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• 제25권6호
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• pp.1499-1506
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• 2014

랜덤워크는 다양한 분야에서 랜덤현상을 기술하는데 이용되고 있으나, 현재까지 개발된 랜덤워크 검정법에는 유의수준 왜곡과 낮은 검정력 등의 문제가 있는 것으로 알려져 있다. 이러한 문제점들을 개선하기 위해 Kim 등 (2014)은 부호검정에 기초한 랜덤워크 검정 (${\rho}=1$)방법을 제안하였다. 본 논문에서는 보다 개선된 랜덤워크 검정법을 제안하고자 부호검정보다 검정력이 우수한 것으로 알려진 윌콕슨 부호순위검정을 이용한 랜덤워크 검정법을 제안하고, 모의실험을 통해 부호검정, 윌콕슨 부호순위검정, 확장 Dickey-Fuller 검정의 성능을 비교하였다. 모의실험 결과 소표본에서 비모수 검정기법들이 ADF 검정보다 우월하다는 사실을 재확인하였다. 새롭게 밝혀진 사실은 부호검정이 윌콕슨 부호순위검정에 비해 높은 검정력을 가지며, 또한 비모수 검정기법들은 ${\rho}$가 양의 부호를 가지는 경우 (0 < ${\rho}$ < 1) 정규분포보다 이중지수분포에서 낮은 검정력을 가지게 되나, ${\rho}$가 음의 부호(-1 < ${\rho}$ < 0)를 갖는 경우에는 정규분포보다 이중지수분포에서 높은 검정력을 보인다는 사실이다.

• Journal of Advanced Marine Engineering and Technology
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• 제29권1호
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• pp.17-24
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• 2005

The characteristics of diesel spray have effect on the engine Performance such as power. fuel consumption and emissions. Therefore, This study was Performed to investigate the effect of various injection parameters. In this study. the experiment is performed by using the high temperature and high pressure chamber. Spray behaviors are visualized by using the high speed camera and spray angle. Penetration etc. are measured. Experimental results are summarized as follows ; 1) Correlations of spray Penetration is expressed as follows $$0 $$t_b 2) Correlations of spray Angle is expressed as follows $$T_a=293K \;;\; tan({\theta}/2)=0.59({\rho}_a/{\rho}_f)^{0.437}$$ $$T_a=473K\;;\; tan({\theta}/2)=0.588({\rho}_a/{\rho}_f)^{0.404}$$ 3) The measured macro characteristics - spray tip penetration and spray angle agreed well with established correlations.

• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1321-1328
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• 2005

The characteristics of the diesel spray have affected certain aspects of engine performance, such as the power, fuel consumption, and emissions. Therefore, this study was performed to investigate the effects of various injection parameters. In order to obtain the effect of injection parameters on diesel spray characteristics, the experiment is performed by using a high temperature and pressure chamber. The behaviors of the spray are visualized by using a high speed video camera, spray angle, penetration, and various other things. The results of the experiment are summarized as follows. (1) The correlation of the spray penetration can be expressed as follows. $$0< t $$t_{b} (2) The correlation of the spray angle can be expressed as follows $$T_a=293K\;tan({\theta}/2)=0.59({\rho}a/{\rho}f)^{0.437}$$ $$T_a=473K\;tan({\theta}/2)=0.588({\rho}a/{\rho}f)^{0.404}$$ (3) The measured macro characteristics that include the spray tip penetration and spray angle corresponded with the established correlations.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.610-615
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• 2015

In order to study and obtain the mathematical relation between the electrification degree of transformer oil flow and the electrostatic current, a small amount of data about the electrification degree of oil flow and the corresponding electrostatic current is studied by linear regression method and grey model method. The results show that the linear correlation between the electrification degree and the electrostatic current was not good, and the relation between the electrification degree of oil flow and electrostatic current (i) could be expressed as ${\rho}(0)=0.2049\;i^{(0)}+169.4419$ according to grey model GM (0, 2) when the electrification degree of oil flow is represented by the charge number generated from transformer oil per unit volume, namely the charge density (${\rho}$).

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.182-185
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• 2003

Proposed Hybrid System is composed of phase leading capacitor banks, LC passive filters and active power filter. The passive power filter in parallel connection eliminate the 5th and 7th harmonics. The Variable capacitor banks correct the most of power factor, and the active power filter takes charge of remainder,

• Journal of applied mathematics & informatics
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• 제5권3호
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• pp.877-888
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• 1998

We show that if dialation operator $\parallel\sigma_r\parallel\; E=\Psi(r)$ of E, then $\Lambda_\subset_{\Psi1}E\subset\;M_\Psi$, We also show that there are lattice-isomorphic copies of $l_\rho \; and \;l_\infty$ in $M \Psi$ under some condition.